1. Field of the Invention
At least one embodiment of the invention relates to a permanently or temporarily implantable device having an elongated electrical conductor.
2. Description of the Related Art
Such devices, for example electrode lines for electrostimulation, have the disadvantage that their electrical conductor may heat up during magnetic resonance imaging due to the fact that the alternating magnetic fields that are present induce considerable electrical currents in the electrical conductor. In addition, such induced currents may be delivered to surrounding tissue via electrode poles of the electrode line, resulting in undesired heating of the tissue, for example. For this reason, there is presently little or no possibility for cardiac pacemaker patients to be tested using magnetic resonance imaging.
Implantable cardiac pacemakers or defibrillators (also jointly referred to below as cardiac stimulators or implantable pulse generators (IPG)) are typically connected to at least one stimulation electrode line, which at its proximal end which is provided for connection to the cardiac pacemaker or defibrillator has a standardized electrical terminal, and at its distal end which is provided for placement in the heart has one or more electrode poles. Such an electrode pole is used to deliver electrical pulses to the (myocardial) tissue of the heart or for sensing electrical fields in order to sense an activity of a heart. For these purposes, electrode poles typically form electrically conductive surface sections of an electrode line. Electrode poles are typically provided as an annular electrode in the form of a ring around the electrode line, or in the form of a point electrode or tip electrode at the distal end of the electrode line. At their proximal end the electrode poles are connected in an electrically conductive manner via one or more electrical conductors to contacts of the electrical terminal of the electrode line. Thus, the electrode lines at their proximal end extend between the contacts of the electrical terminal, and at the distal end one or more electrical conductors which electrically connect the one or more electrode poles to the one or more contacts extend between the electrode poles. These electrical conductors may be used on the one hand for transmitting stimulation pulses to the electrode poles, and on the other hand for transmitting electrical signals received via the electrode poles to the proximal end of the electrode line, and in the description below are also referred to in each case as a function line. Such function lines are electrical conductors which are necessary for the functions of the particular electrode line, and are thus subject to the risk of electrical currents being induced therein as the result of external alternating magnetic fields which, for example, may lead to undesired heating of the function lines or the electrode poles connected thereto, or may result in the discharge of corresponding currents via the electrode poles to surrounding tissue, and thus heating of the surrounding tissue.